In recent years, the types of networks to which a mobile station can connect have been diversified along with the advancement of radio communication technologies. Examples of the networks to which a mobile station can connect include: (1) the third generation radio communication network; (2) the next generation radio communication network; (3) WLAN specified in IEEE802.11, (4) WiMAX specified in IEEE802.16 and the like; and so forth.
In addition, on the assumption that a mobile station is connectable to multiple networks, a technique to switch a network to which the mobile station connects from one to another (handover technique) has been also proposed (3GPP TR23.882 V1.9.0 (Section 7.8.2), for example).
The aforementioned switching (handover) of the network is performed in a case where a communication quality is deteriorated in the network to which the mobile station connects, or the like, for example.
Here, a bearer that can be set up with the mobile station and each type of network is dependent on the capabilities of the type of network and the mobile station. For this reason, the number of bearers that can be set up with the mobile station and each type of network differs from one network to another.
Accordingly, in the aforementioned handover, there may be a case where the number of bearers that can be set up with the mobile station and a handover source network is larger than the number of bearers that can be set up with the mobile station and a handover destination network.
In the aforementioned case, the handover destination network cannot take over the service provided in the handover source network. In sum, along with the diversification of the types of networks to which the mobile station can connect, it is expected that a handover cannot be appropriately performed.